A cellular telephone built on a mobile computing platform, sometimes referred to as a smartphone, includes computing and communication resources that enable a software application running on the smartphone, for example a web browser, to access and interact with Internet web pages and other data sources. A cellular telephone lacking some of the computing and communication enhancements included in a smartphone, for example a phone lacking a web browser, may be referred to as a “feature phone.” Smartphones may be capable of executing software applications such as interactive calendars, games, and other general-purpose applications selected and installed by the smartphone's user. However, some software applications on a smartphone may be unavailable for use while the smartphone is sending or receiving voice calls. Some software applications may interfere with sending or receiving a voice call on a smartphone while an application is running. Some software applications may be difficult to control or view on the relatively small displays provided on some smartphones. Controlling an application or reading the smartphone's display may be impractical or inconvenient while a voice call is in progress. Some users may therefore prefer to run some software applications on a portable personal computer, which generally has a larger, higher-resolution display than a smartphone, especially when a user desires to conduct voice communications while operating a software application. Some users may prefer a full-size keyboard and cursor control device connected to a personal computer over soft keys or small keypad buttons on a smartphone, for example when a large number of characters are to be typed, fine control of a cursor on a display is important, or data entry accuracy is important.
Cellular modems are available for sending and receiving data, for example documents, Internet email, email attachments, RSS feeds, audio files or streams, video files or streams, and the like over a cellular telephone network. A cellular modem may be an integral part of a personal computer or may be an external device which connects to an interface port on the personal computer, for example a USB port. A smartphone or a personal computer with an internal cellular modem or connected to an external cellular modem may be operable as a wireless LAN access point, sometimes referred to as a “WiFi hotspot”, for example to enable other devices to access the smartphone or cellular modem's Internet connection or to form an ad hoc network. However, a smartphone may not be operable for placing or receiving telephone calls for voice communications (also referred to as “voice calls”) while operating as a WiFi hotspot. A user may find it inconvenient to send or receive voice calls while a smartphone is connected by an electrical cable to a personal computer. Establishing data communication between a smartphone and a personal computer, sometimes referred to as “tethering”, may not be possible if a suitable interconnecting electrical cable is not available or has been left behind or misplaced.
A Subscriber Identity Module (SIM) stores identity and authentication data in an electronic device used by a subscriber to a cellular telephone network. A SIM is an integrated circuit that may be provided in a standardized package referred to as a SIM card. A SIM card may be placed inside a cellular phone or portable computer to protect the SIM card from damage by impact, flexure, electrostatic shock, and circuit damage from dirt and other contaminants, and to enable the device holding the SIM card to communicate with a cellular telephone network. For example, a cellular telephone may be provided with a cavity adapted to receive a SIM card. An electrical connector in the cavity and a corresponding mating connector or contact pads on the SIM card enable data communication between the SIM card and other components in the cellular telephone. The cavity holding the SIM card may be covered by a removable battery or a detachable cover. A SIM card may comply with one or more electrical and mechanical standards, for example standards published by ISO/IEC, ETSI, JEDEC, or others. SIM cards may be provided in different standard sizes, some of which are referred to as full-size, mini-SIM, micro-SIM, nano-SIM, and embedded SIM.
A SIM card may be transferable from a cellular telephone to another cellular-enabled device, for example another cellular telephone, a cellular modem, or a personal computer. However, a cellular telephone or smartphone may be unable to send or receive voice calls or other data after the SIM card has been removed from the phone.